With rapid increase of data services, data transmission pressure borne by carriers on a licensed spectrum is higher and higher. Therefore, sharing of data traffic in a licensed carrier by a carrier of an unlicensed spectrum becomes an important evolution direction of subsequent long-term evolution (LTE) development.
The unlicensed spectrum has characteristics as follows. The unlicensed spectrum should not be purchased, cost of spectrum resources is zero, and the unlicensed spectrum has characteristics of free or low charge. Individuals and enterprises may participate in deployment, and equipment of equipment manufacturers may be deployed at random and has characteristics of low access requirement and low cost. Frequency bands of 5 GHz, 2.4 GHz and the like in the unlicensed spectrum may be used and have a characteristic of great available bandwidth. The unlicensed carrier has a resource sharing characteristic, that is, during operations of multiple different systems or during operations of different operators in the same system, some resource sharing manners may be considered to increase spectrum utilization efficiency, and the like.
Based on the above characteristics of the unlicensed spectrum, a Rel-13 version of an LTE system was started to be researched in September 2014, wherein an important research issue is that the LTE system is operated by using carriers of the unlicensed spectrum. This technology enables the carriers of the existing unlicensed spectrum to be used by the LTE system, and potential spectrum resources of the LTE system are greatly increased, so that the LTE system may achieve a lower spectrum cost.
Based on various benefits brought by unlicensed carrier resources used by the LTE, a Licensed-Assisted Access (LAA) system should consider fair coexistence with other technologies (such as, Wireless-Fidelity, Wi-Fi) while using the unlicensed carrier. In addition, with respect to access of the unlicensed spectrum, a Listen Before Talk (LBT) mechanism is required to be executed for controlling in some areas. Therefore, LAA equipment, such as at least one of an evolved Node B (eNB) or a User Equipment (UE) should comply with LBT requirements, thereby achieving friendly coexistence with the Wi-Fi system.
An agreement on frequency reuse is reached in a Rel-13 RAN1 # Ad-hoc conference, that is, realization of frequency reuse during transmission of adjacent LAA cells under the same operator is a goal of LAA design, and design of the LBT should be considered. For a terminal side, terminals in the same cell or terminals under the same operator should also consider the reuse problem, and similarly, design of frequency-domain patterns during corresponding LBT detection should be considered, thereby realizing or increasing multiplexing efficiency.
However, in a Rel-13 RAN1 #80bis conference, with respect to a base station side, when the LBT mechanism is applied to competitive channel access in an LBE (load-based equipment) manner, candidate methods capable of increasing downlink transmission multiplexing efficiency include: Clear Channel Assessment (CCA) threshold adaptation, Tx start timing alignment, signal subtraction from ED or modified ED, and combination of those options or other alternatives are not precluded. Based on advantages and disadvantages of several methods above discussed in each conference before the 82nd conference, finally an agreement is reached as follows: frequency reuse on the base station side is increased in the manners of CCA threshold adaptation and Tx start timing alignment. Based on this, with respect to a CCA threshold adaptation method, the LAA equipment needs to recognize that signals sensed by the unlicensed carriers come from other LAA equipment or other system equipment, thereby adjusting (increasing or decreasing) a CCA detection threshold to realize equipment multiplexing under the same operator. However, with respect to a Tx start timing alignment method, in order to allow different LAA equipment of the same operator to align at transmission timing points, self-delay is introduced, and/or, the LBT process is coordinated (coordination parameters include at least one of the followings: a random back-off value N, a start timing position of an Extended Clear Channel Assessment (ECCA) or transmission starting timing), but channel access probability is decreased, so that good multiplexing cannot be realized.
With respect to problems in related arts that multiplexing efficiency is low and brought unlicensed carrier access probability is low because an interference source problem cannot be recognized during CCA detection, and no effective solution has been proposed at present.